(1) Field of the Invention
The present invention relates generally to mechanical pencils and, more specifically, to a side knocking-type writing instrument in which a writing component can be protruded from a front end of a barrel only by pressing a knocking member disposed at a side face of the barrel.
(2) Background of the Invention
As a knocking-type mechanical pencil or a knocking-type ballpoint pen, a side knocking-type writing instrument in which protrusion and retraction operations of a writing component are made with a knocking member, such as a knocking button disposed on the side face of a barrel, has been known. In a conventional side knocking-type writing instrument, a sloped cam system has been used wherein, as described in U.S. Pat. No. 3,883,253, a sliding member is housed in a barrel in such a state that the sliding member is biased backwardly by a spring, a sloped cam is formed on the sliding member and a pressing portion of the knocking member is forced to abut on the sloped cam by which the sliding member is moved forward against the spring.
In the foregoing sloped cam system, the pressing force from the knocking member has a force component directed in the axial direction which contributes to the forward movement of the sliding member and a force component directed in the radial direction which presses the sliding member perpendicularly against the barrel. The force in the radial direction turns into a strong frictional resistance when the sliding member moves. However, when the sliding member moves forward, the spring is compressed, and the resilient power of the spring becomes large. Accordingly, the frictional resistance is even stronger and the knocking load increases, leading to a drawback that the conventional side knocking-type writing instrument cannot be operated with a small pressing force.
Japanese Utility Model Publication B-3-56387 discloses a side knocking-type mechanical pencil which is not operated by means of a sloped cam system. The knocking-type mechanical pencil disclosed in this publication has a mechanism wherein a push button is pressed so as to buckle each of intermediate hinge portions forwardly in an axial direction at a front linking position and a rear linking position of linking elements, thereby moving a lead chuck forwardly in the axial direction and feeding a lead. However, this mechanism has a complicated structure for buckling the intermediate hinge portions, whereby the number of parts is considerably increased, such being unfavorable from an economical standpoint. Further, it is also impossible to accommodate plural leads in the lead chuck.
U.S. Pat. No. 3,558,233 discloses a writing instrument wherein a cam is pivotably mounted on a barrel, and a sliding member is moved forward by rotating the cam by means of a knocking member. However, in this type of writing instrument, since the cam is fixed to the barrel with a rotating shaft and cannot be entirely transferred in an axial direction, the movement of the sliding member in the axial direction is restricted to the range of rotation of the cam and, therefore, it becomes difficult to increase the range of movement of the sliding member. Accordingly, in order to secure a desired predetermined movement of the sliding member in the conventional writing instrument, the movement of the knocking member is required to be large or the cam is required to be formed on a large scale, whereby the structure of the writing instrument becomes complicated.
The present invention overcomes many of the disadvantages inherent in conventional side knocking-type writing instruments.
It is an object of the present invention to provide a side knocking-type writing instrument which is simple in construction and in which the knocking operation of the knocking member can be effected with a small pressing force.
It is another object of the present invention to provide a side knocking-type writing instrument in which the sliding member can be slid within a large range of movement when the knocking member is knocked.
Still another object of the present invention is to provide a side knocking-type writing instrument which is easy to be assembled, simple in construction and can be manufactured at a low cost.
In order to accomplish these objects, there is provided according to the present invention a novel and improved side knocking-type writing instrument having a barrel having a longitudinal axis, a front end, and a rear end. A sliding member has a writing component and is disposed in the barrel for undergoing forward and rearward sliding movement along the longitudinal axis. A knocking member is disposed on a side surface of the barrel for undergoing movement in a direction transverse to the longitudinal axis of the barrel. A linking pawl is disposed between the knocking member and the sliding member for undergoing pivotal movement therebetween and axial movement along the longitudinal axis. The linking pawl has an outward end disposed in contact with a pressing portion of the knocking member and an inward end disposed in contact with a shoulder of the sliding member. When the pressing portion of the knocking member is pressed, the knocking member undergoes movement in the transverse direction so that the linking pawl is moved axially while being pivoted and the sliding member is slid forwardly to thereby protrude the writing component from the front end of the barrel.
In one embodiment, the linking pawl is bent in an approximately L-shaped form in side view, and the outward end of the linking pawl is disposed in a seat formed at the pressing portion of the knocking member. In another embodiment, the outward end of the linking pawl is connected to the pressing portion of the knocking member by means of a flexible hinge portion. The shoulder of the sliding member with which the inward end of the linking pawl is contacted is preferably generally L-shaped. The sliding member has a passageway hole in which plural writing components, such as pencil leads, can be accommodated.